Conventionally, IC cards exist that enclose inside them an antenna substrate by sandwiching the antenna substrate between upper and lower core sheet, thermally bonding the outer region which is larger than the antenna substrate, of the core sheet by heating and pressing (e.g. see Patent Literature 1).
However, the thickness of the outer region is less than the thickness of the region in which the antenna substrate is laminated, by the thickness of the antenna substrate. Therefore, in the outer region, a gap is formed between the upper and lower core sheets that causes insufficient heating and pressing. As a result, a defect-like recess is formed or the shape of the outer peripheral edge of the antenna may appear on the card surface, which causes a problem in external appearance. To solve the problem, pressing is required for a long period of time, which causes deterioration in production efficiency.
[Patent Document 1] Japanese Unexamined Patent Application, Publication No, 2007-272806